Today I finally 'got there' with my Shark .15 combo. The past few years I have been going retro a bit. I've been able to find kits of some of the planes I built 40+ years ago and enjoying them. I looked for years trying to find a Shark .15 on the bay and then noticed that Walt Umland makes the kit. Got it. Beautiful. Built it. Looks great. Weighs one pound, no flaps. Since my original Shark had a Fox and I had one, that's what is up front.
First flight with Master 7x5 the motor was screaming and the nose was a blur. Not good. Next I tried an APC 7x6w. Much better, it held the revs down so the nose was not buzzing. The gas tank is the perfect long skinny 2 oz. job with uniflo. Unfortunately 2 oz. was not enough to do a pattern. Also not much room up front for a bigger tank. There have been several outings this winter and to shorten the story a bit here is where we are now. The .15x is a hot little motor and the early ones were supplied with a .040 head shim. I found that mine did not have that so I added an extra .010 shim to ease the compression a bit. Todays outing had a Master 8x5 Scimitar and a venturi reducer ( .250 vs .270) and a spraybar from a later model Fox .15bb.
Result: Smooth 5 3/4 minute run time at 4.6 sec. on 58 ft. .012 lines. Full pattern with crisp corners. Me happy! Sure, I could have used an LA but really enjoyed getting it to run properly in full nostalgia mode!! TS